Sustainable Agriculture Activity Guides Earthworms 3.1

Earthworms

Build Soil Fertility

Overview

The fertility of a soil can be defined as its capacity to produce crops and is dependent on

many physical, chemical and biological properties of the soil. Earthworms can play a

significant role in enhancing soil fertility and plant productivity in a number of direct and

indirect ways.

Earthworm activity can enhance soil nutrient cycling, the activity of other beneficial soil

organisms, and soil physical properties, such as soil structure and tilth. Since farming can

involve many soil disturbing activities, understanding the biology and ecology of

earthworms and other soil biota can help inform management decisions that may impact

soil biota and crop performance. The following reference resources are provided to

improve your familiarity with the topic.

Resource References

Earth Worms: The Agriculturalist’s Friends, by Jennifer A. Ramsay and Stuart Hill.

Macdonald Journal 39(10), 6-8 Oct. 1978. www.eap.mcgill.ca/publications/eap6.htm

Earthworms Science Page, Garden Mosaics. Cornell University

www.gardenmosaics.cornell.edu/pgs/science/english/earthworm.htm

Invertebrate Identification Guide. University of Michigan

http://www.biokids.umich.edu/files/20491/InvertIDGuide2004.pdf

The Worm Book: The Complete Guide to Gardening and Composting with Worms,

Nancarrow, by Loren, and Janet Hogan Taylor. Berkley: Ten Speed Press, 1998.

Worms Eat Our Garbage, by Mary Apelhof, Mary Frances Fenton, Barbara Loss

Harris, and Daniel L. Dindal. Flowerfield Press, 1993.

Sustainable Agriculture Activity Guides Earthworms 3.2

Earthworms

Build Soil Fertility

Introduction

Earthworms crawl through soil consuming organic matter and in the process break it

down (decompose it) and produce worm castings (worm manure), which are rich in

nutrients, humus and microorganisms. In this process, earthworms also mix and aerate

the soil. Together all of these effects help improve numerous soil physical

characteristics. Additionally, the earthworm activity helps make nutrients available to

plants while moderating the soil pH. Activities that impact earthworm behavior include

disrupting the soil (e.g., through tillage and cultivation), and the use of some chemical

fertilizers and pesticides.

In this activity the participants will learn about basic soil ecology using earthworms and

other soil fauna as study organisms. Students will discover which soil conditions and

habitats are best suited for earthworms.. In particular, the participants will be asked to

draw conclusions about which management practices support worm activity based on

how often and in which ways soil is disturbed.

To Lead This Activity You Need to Know

Facilitators of this activity need to have basic understanding of the following concepts in

order to effectively lead students through this activity:

Habitat

Earth worm and soil invertebrate biology

Soil physical properties, including texture and structure

Agricultural soil management

Key Concepts

Soil organisms have special soil habitat needs

Cultivation and other human activities impact soil habitat

Diversity of soil organisms (e.g., invertebrates and microorganisms)

Plants and animals rely on soil fertility and nutrients to be healthy

Soil organic matter

Worm castings (manure)

Earthworms are beneficial to the soil for the following reasons:

1. Castings have near neutral pH (pH 7).

2. Castings are rich in plant accessible nutrients (e.g, high in N, P, K and Mg).

3. Castings provide a home for beneficial microorganisms.

4. Castings have a high percentage of organic matter. This allows the soil to absorb and

hold more water.

5. Castings include mucus produced by the earthworms, which contributes to improved

soil structure.

Sustainable Agriculture Activity Guides Earthworms 3.3

Objectives

Understand that biologically active soils typically contain a variety of

invertebrates, often including earthworms.

These organisms both contribute to and are encouraged by healthy soil structure

and fertility.

Understand that farming practices can impact soil organisms and structure

positively or negatively.

Materials (One of each for each group of 2 – 3 students

shovel

12” X 12” quadrant (can be made from pieces of drip tape, stapled at corners)

light colored cloth, butcher paper, or white plastic trash bags for sorting worms,

insects and other organisms found in the soil

transparent collection container for holding and counting soil organisms

data sheet

pencils

Activities (45-60 minutes)

Earthworm Census

1. Discuss the biology of earthworms and their benefits for the soil. (5 min)

2. Break students into groups of two or three depending on size of group and

supervision. Assign each group one location in which they will take a census of the

earthworms and other invertebrates in a ½ to 1 cubic-foot sample (1 square foot

surface area, ½ to 1 foot deep). Choose different locations that clearly demonstrate

distinct soil quality characteristics. Examples could include a heavily worn and

compacted dirt road, a hedge row or forest edge, a freshly tilled annual vegetable bed,

and a cover cropped orchard. Choose different sampling sites that are as close

together as possible to save time walking between samples.

3. Once at a sampling site, guide students in placing quadrants on the soil surface. Have

students remove soil within the quadrant to a depth of 6-12 inches and place contents

on cloth, butcher paper, or plastic trash bag. (10 min.)

4. Sort earthworms and other invertebrates from the soil, count and place them in the

collection container. (10 min)

5. Have each student group sample from an additional site with distinct soil

characteristics. If you have sufficient time (e.g., more than one hour), you can have

the groups sample three or more locations.

6. After the individual groups have counted the earthworms and other invertebrates from

each sample site, have students complete the data table and graph on the student work

sheet. (10 min.)

Sustainable Agriculture Activity Guides Earthworms 3.4

Discussion and Reflection (10-15 minutes)

Bring the students together and discuss the implications of their findings. Have them

relate particular soil uses and management practices (e.g., cultivation intensity, annual or

perennial crops, additions of organic matter such as crop residues, leaf litter or compost).

Encourage students to think about the impacts of the type and frequency of soil

disturbances, organic matter or fertilizer additions, and other management practices on

soil properties and potential for plant growth.

Additional Activities for Home or School

Students can be given an assignment to explore various locations and soils to find three

or four locations where they find evidence of worms and other soil invertebrates, and

three of four where they do not. Locations do not have to be agricultural or even

managed. The idea is to encourage students to look at common landscapes and consider

whether the soil provides a good habitat for beneficial soil organisms.

Make sure that the students have permission to dig in these areas and then have them use

the same sampling process as before to make observations. Have students describe the

soil conditions they find at each site and guess what management practices might take

place there. You might have the students select half their sites on the school campus and

half in their home landscapes.

Another good way to demonstrate the benefits of earthworms is to build and maintain a

worm bin in the classroom. A worm bin shows how organic material can be turned into

highly fertile vermicompost by using special surface feeding species of earthworms.

Building and maintaining a worm bin requires a moderate investment of time and

resources. Worm bins and worms can be purchased from various suppliers.

Sustainable Agriculture Activity Guides Earthworms 3.5

Student Work Sheet Earthworms

Name(s): Build Soil Fertility

Date:

Location:

Earthworms Other Invertebrates

Collection

Site # Tally here

Final

Count Tally here

Final

count Soil/Site Description

1

2

3

4

5

6

7

8

9

10